Building construction commonly involves flashing and sealing of openings in the exterior surface of a structure, where fenestration products such as windows, doors, skylights, and vents are located, to prevent moisture or air from entering the envelope of the structure. To water/weather-proof such openings, various types of flashing products have been developed which are installed at the openings and surrounding the fenestration products. One such flashing product includes strips of self-adhered flashing often sold in rolls and made of asphalt, rubber or similar materials. These strips of self-adhered flashing are commonly adhered to the sheathing and wrapped into the opening at the framing surface of the opening, or adhered to the sheathing and placed over the edges, “fins,” or frames of the fenestration product. The opening in the exterior of the structure is typically described as having a bottom edge (the sill), a top edge (the head), and the vertical side edges (the jambs). The self-adhered flashing products have significant disadvantages. These flashings come in rolls of material, typically field cut into strips. The flashing strips do not form a continuous membrane surface, as they rely on adhesion and proper lapping to prevent water and air intrusion at the joints between the flashing strips and to prevent gaps and openings at the corners of the fenestration products and the openings. In particular, openings have historically suffered from leaks due to defects in the installation of the flashing as well as the inherent difficulty of water/weather-proofing the three dimensional corners of openings with flat or folded strips of flashing. The flashing strips are flat and are not manufactured to a three dimensional shape. The flashing can be folded into an opening, but inherent waterproofing problems result where the flat or folded strips meet the corners of the opening. In addition, due to the flat nature of the flashing products, the flashing material itself does not form returns, or back dams to reduce the infiltration of water and/or air at the opening.
Another flashing application for openings includes the use of spray, roll, or brush applied water/weather-proofing products that coat the opening in an attempt to provide complete water/weather-proofing of openings without seams or joints. These fluid applied flashing systems also have significant disadvantages including the propensity of the fluid applied flashing to crack at the corners of the opening as the material dries or is stressed due to thermal movement of the building and openings. To reduce this cracking or breaches in the fluid applied flashing, some products also recommend the use of a separate flat reinforcing mesh tape, typically made of fiberglass, to reinforce the membrane. The mesh tape, like the above described flashing strips, comes in rolls and thus does not form a three dimensional shape to reinforce the corner or to provide a backing for flashing returns, or back-dams. In addition, these fluid applied systems do not include, within the flashing material itself, returns, or back-dams to reduce the infiltration of water and/or air at the opening. The likelihood of moisture and air intrusion at openings is greater in openings that do not include back dams to limit the passage of air or water and to re-direct water back to the exterior.